Roll out on a floured surface a puff pastry leaf. Sprinkle the whole surface of the leaf with the grated parmesan and the freshly grated pepper and spread the prosciutto slices.
Fold into triangles - enclosing the prosciutto. Fold the two edges in such a way so that they have the shape of the croissant. With a brush, dipped in the slightly beaten egg, daub the surface of the croissants. Sprinkle over them the grated grana cheese (or kefalotiri) and bake them in the oven at 325 ° for about 20 minutes.